RADHIKA. S (119)

SIGNIFICANCE OF MANGROVE ECO-SYSTEM

INTRODUCTION

The term “mangrove” refers to an assemblage of tropical trees and shrubs that grows in the intertidal zone (Tomlinson, 1986).  Mangroves are commonly found along sheltered coastlines in the tropics and subtropics where they fulfil important socio-economic and environmental functions. These include the provision of a large variety of wood and non-wood forest products; coastal protection against the effects of wind, waves and water currents; conservation of biological diversity, including a number of endangered mammals, reptiles, amphibians and birds; protection of coral reefs, sea-grass beds and shipping lanes against siltation; and provision of habitat, spawning grounds and nutrients for a variety of fish and shellfish, including many commercial species.

Terms such as mangrove community, mangrove ecosystem, mangrove forest, mangrove swamp, and  are used interchangeably to describe the entire mangrove community.

Mangroves have traditionally been widely used and exploited in the past in the majority of countries in which they exist. Knowledge of their current and past extent, condition and uses is essential for forest managers and policy- and decision-makers. The major controls on mangrove distribution are climate, salinity, tidal fluctuation, sedimentation, and wave energy.

         

Mangroves include approximately 16 families and 40 to 50 species. Although once thought of as unproductive, transitional systems, mangrove swamps are now viewed as highly productive, ecologically important ecosystems (FAO, 2003).

Economic Benefits

The mangroves supply forestry products (firewood, charcoal, timber, honey

etc.) and fishery products (fish, prawn, crab, mollusk etc.). Due to high

calorific values, mangrove twigs are used for making charcoal and firewood. The mangrove wood with high content of tannin is used as timber for its durability. The pneumatophores are used to make bottle stoppers and floats. Shells of mangrove molluscs are used to manufacture lime.

Mangroves attract honey bees and facilitate apiculture activities in some

areas. For instance, the Sundarbans provide employment to 2000 people

engaged in extracting 111 tons of honey annually and this accounts for about 90% of honey production among the mangroves of India (Krishnamurthy,l990).

Ecological Significance

Although early workers regarded mangrove forests as unimportant, transitional communities with a low productivity, most ecologists today view them as highly productive, ecologically important systems. 

Mangrove swamps act as traps for the sediments, and sink for the nutrients. The root systems of the plants keep the substrate firm, and thus contribute to a lasting stability of the coast. The ecosystem provides a source of food, breeding grounds and nurseries for many food fishes and shellfishes, and they do very often encourage and attract other kinds of wildlife. They are known to remove CO2 from the atmosphere through

photosynthesis. This perhaps reduces the problems that go with the ʹgreen

house gases’ and global warming.

Mangroves are known to remove CO2 from the atmosphere through

photosynthesis. This perhaps reduces the problems that go with the ʹgree

house gases’ and global warming. They fix greater amounts of CO2 per unit area, than what the phytoplankton do in the tropical oceans (Kathiresan &Bingham, 2001). The mangroves are capable of accumulating and storing carbon in the soil in large quantities.

Supporting the fishes and wildlife populations

          Mangrove ecosystems are important for fish production. They serve as nursery, feeding and breeding grounds for many fishes and shellfishes.

          Nearly 80% of the fish catches are directly or indirectly dependent on mangrove and other coastal ecosystems worldwide (Kjerfve &

Macintosh, 1997). To cite a specific case, the Pichavaram mangroves

alone nurture 30 species of prawns, 30 species of crabs, 20 species of

mollusks, and 200 species of fish (Kathiresan, 2000b).

          It is widely believed that the mangroves are like the roots of the sea and, if there are no mangrove forests along the coast, there will be either no fish or fewer fish in the sea and the sea will act like a tree without roots. Besides fish, the mangroves support a variety of wildlife such as the Bengal tiger crocodiles, deer, pigs, snakes, fishing cats, insects and birds.

Conclusion

Even though mangroves have been often used for the collection of wood forest products and as a source of subsistence for local populations, wood removal is rarely the main cause of loss. Human pressure on coastal ecosystems and thus competition for land for aquaculture, agriculture, infrastructure and tourism are often intense and are among the major causes of the reported decrease in these forest areas over time.

On a positive note, integrated coastal area management has been identified as a possible solution to competing land uses in several countries.

REFERENCES 

FAO. 2003. Status and trends in mangrove area extent worldwide, by M.L. Wilkie and S. Fortuna. Forest Resources Assessment Working Paper No. 63. Rome. (available at www.fao.org/forestry/mangroves/statistics).

Krishnamurthy, K. (1990). The apiary of mangroves. In: ‘Wetland Ecology and management: Case studies’ (D.F. Whigham, D. Dykyjoya & S.

Hejnyeds), pp. 135‐140. Kluwer Academic press, Netherlands.

Tomlinson, P.B. 1986. The botany of mangroves. Cambridge, UK, Cambridge University Press.